This invention relates generally to a method and device for introducing a liquid sample into a small diameter column and more particularly to a method and device for on-column injection of a liquid sample into a capillary column with inside diameter less than 200 microns.
Columns of increasingly smaller diameters have been used for gas chromatography. The advantages in using small diameter columns for trace analysis have been described, for example, by J. Hinshaw (5th International Capillary Symposium, Riva Del Garda, 1984). Wall-coated open tubular columns with internal diameters of 100 microns are now commercially available. Flame based detectors such as flame ionization detectors and flame photometric detectors generally provide acceptable performance when using these narrow diameter columns. A new design for an electron capture detector compatible with columns with internal diameters of 100 microns has been disclosed recently by G. Wells and R. Simon (High Res. Chrom. & Chrom. Comm. 6 (1983) 427 and 651) while the use of the split-splitless injection techniques and cold on-column injection with such columns was discussed by Onuska (J. of Chromatogr., 289 (1984) 207). Although the advantages of cold sample introduction into the column are well known in terms of mass discrimination and inertness, the conventional method of using a thin needle to place the sample inside a capillary column has the disadvantage of being limited to columns of inside diameters of about 200 microns or greater since the outer diameter of the needle must necessarily be smaller than the inside diameter of the capillary column. The inside diameter of such a thin needle would be too small and hence impractical. Moreover, a needle with outside diameter not much smaller than the inside diameter of the capillary column may easily scratch the inside of the column when placed directly inside.